Recently, touch sensors are being widely applied to various electronic products such as mobile phones, personal digital assistants (PDAs), and handheld personal computers where technique for manufacturing capacitive touch sensors is most widely used.
The touch sensors are mostly a kind of capacitive touch sensors comprising a single electrode layer on a glass substrate.
Generally, conventional capacitive touch sensors comprise a touch sensing electrode layer made of indium tin oxide (ITO).
For example, the ITO is directly provided on a glass substrate by sputtering and then patterning is carried out to form a pattern of a touch sensing electrode layer.
The pattern of the touch sensing electrode layer includes an X-axis sensing electrode pattern and a Y-axis sensing electrode pattern, and one of them may include a conductive layer so as to form a bridge structure that one axis of the sensing electrode pattern passes across the other axis thereof.
Also, for insulation of the X-axis sensing electrode pattern and the Y-axis sensing electrode pattern, an insulating layer is formed at the position that the X-axis sensing electrode pattern and the Y-axis sensing electrode pattern crisscross with each other.
Such a touch sensor includes, as shown in FIG. 1, a transparent substrate 10 having an active region 11 and an inactive region 12 corresponding to the periphery of the active region 11, and an electrode unit formed on one surface of the transparent substrate 10.
The transparent substrate 10 may act to provide a region in which the electrode unit for detecting a touch position is formed. The transparent substrate 10 should have force for supporting the electrode unit and transparency to allow a user to perceive images provided from an image display device.
Thus, the touch sensor may include the active region 11 and the inactive region 12 corresponding to the peripheral region of the active region 11.
The active region 11 refers to the part that a touch activity of the user is conducted, and corresponds to a display region allowing the user to visually monitor operation scenes of a device.
Also, the inactive region 12 is an unexposed region which is hidden by a bezel portion formed on the transparent substrate 10.
The bezel portion has a shield layer, a protective layer, and an insulating layer formed thereon with a predetermined thickness or more, which are disposed in the periphery of the active region 11, the shield layer for shielding light from a backlight, the protective layer for protecting a lower pattern, and the insulating layer for insulation from upper electrode lines.
These layers are formed to have a thick-film pattern with a predetermined thickness of 10-20 μm or more, and the thick-film pattern may have a desired thickness through repeated coating processes, not a single coating process.
As shown in FIG. 2, when the thick-film pattern is formed by repeating at least three coating processes for stacking with the same pattern widths, an inclined angle at a taper region A of the thick-film pattern is greater than or equal to 20°, causing the flow of a photoresist, as shown in a region B, during a subsequent photolithography process.
The flow of the photoresist causes a disconnection and a defective pattern in a subsequent process.
In particular, the thickness and pattern width of the thick-film pattern are changed by a large inclined angle at the taper region A to cause quality defects in a device, thereby significantly reducing a yield.
FIG. 3 illustrates the occurrence of a disconnection in a subsequent process after the formation of a thick-film pattern according to the prior art as mentioned above.
Therefore, there is a demand for developing a new thick-film pattern structure and the preparation thereof to solve problems in the formation of the thick-film pattern according to the prior art.